Sound amplifier



May 28, 1929.

J. ANDERSON SOUND AMPLIFIER.

Filed Dec. 15, 1926 2 Sheets-Sheet y 28, 1929- J.'N. ANDERSON 1.715181 SOUND AMPLIFIER Filed Dec. 15, 1926 2 Sheets-Sheet 2 Patented May 28, 1929.

UNITED s raras am oFF cE.

JOHN N. ANDERSON, OF CHICAGO, ILLINOIS.

sounn AMPLIFIER.

Application filed December 13, 1926. Serial No. 154,524.

' strument which is being reproduced, that note will be greatly magnified. The presence of this fundamental note in the amplifier is objectionable because it detracts from the pure tones of the reproducer.

The main objects of this invention are to provide improved means for eliminating the timbre of the amplifying mechanism from the tone of sound reproducers such as phonographs and radio receiving sets; to provide a sound amplifier of this kind having a fundamental note outside the range of the human ear; to provide a sound amplifier which is of sufficient length to produce a fundamental note below the average human range; and to provide a sound amplifier of this kind which is compact so as to be adapted for use in phonograph and radio cabi-' nets.

An illustrative embodiment of this invention is shown in the accompanying drawings wherein:

Figure 1 is a vertical section of a phonograph to which an improved sound amplifier has been applied, the latter being shown in elevation and partly in dotted outline.

Fig. 2 is a vertical section of the phonegraph cabinet showing the interior of the amplifier. V

Fig. 3 is a front elevation of the same, part of the hinged doors being broken away for the sake of clearness.

Fig. 4; is a horizontal section, taken on the line ir-4 of Fig. 2.

The fundamental tone of any sound amplifier of the horn type is dependent upon the length of the air passage. The wave length of the fundamental tone is substantially twice the length of the passage and its frequency is calculated by dividing the speed of sound by the wave length. For such calculations, the speed of sound may be considered as eleven hundred feet per second. The lowest musical sound WhlCl). the average human ear can hear has a frequency of approximately fifty vibrations per second.

By constructing a sound amplifier of sufficient length, its fundamental note may be made below the range of the average human ear so as to thereby be eliminated from the tone of the reproducer. By eliminating the fundamental note of the amplifier, its timbre is also eliminated. In the form shown, the improved amplifier is applied to a phonograph comprising the usual upright cabinet 1, which supports a stylus arm 2, on which is mounted a sound reproducer 3 adapted to coa'ct'with a record disc l'supported on a table 5 which is rotated by a motor, not shown, located in a housing 6.

The cabinet 1 comprises the usual walls 7,

hinged doors 8 and hinged top 9.

In the construction shown, the improved amplifier is in the form of a separate sound box unit which is placed inside of the cabinet. The amplifier herein shown is of the horn type and comprises a conduit 10 provided with a tapered passage and having its inlet 11 arranged in communication with the sound reproducer and its outlet end formed to provide a bell 12, which is adapted to be closed by the doors 8.

In the form shown, the conduit 10 includes an upright'section 13, adjacent the inlet 11, which communicates at its lower end with an intermediate section wherein the passage is divided into two branches 14, which reunite in one passage in the bell 12.

The bell 12 and intermediate section of the conduit 10 are formed of a pair of substantially vertical side walls 15, slightly converging rearwardly, and a pair of curved walls 16 and 17 Secured to the walls 15 adjacent the lower edges thereof, is a block 18 having a centrally located, inwardly extending partition 19 which divides the passage at this point into the two branches 14. Spaced from the partition 19, and arranged on respectively opposite sides thereof, is a pair of partitions 20 which are also slightly convergent rearwardly. Arranged between the wall 17 and the partitions 19 and 20, is a substantially horizontal filler block 21.

Mounted at'the rear of the branch passages 14, is a hollow partition member 22 having a pointed head 23 which projects upwardly into the bell 12.

The wall 17 is shaped so as to also provide a housing which may be used as a storage compartment for a radio receiving set 24:. When the device is used for radio purposes, the forward part of the wall 17 may be in the form of a removable panel which provides a mounting for the usual dials 26. The receiving set 22 may be connected with the inlet end 11 of the amplifier by means of a conduit 27. I

In operation, the sound from the reproducer 3' or 24 enters the amplifier at the inlet 11 and passes downwardly through the section 13. In the intermediate portion of the passage, the sound waves travel through the two passages 14 and, after passing the head 23 of the partition 22, they are reunited in the bell 12. The amplifier is preferably of sufficient length to provide a sound passage over ten feet in length so as to produce a fundamental note of low frequency' By the improved form and arrangement of parts herein shown, it is possible to make the sound passage of the desired length and still have an amplifier which is sufficiently compact for use in connection with phonographs and. radio receiving sets.

Although but one specific embodiment of this invention has been herein shown and described, it will be understood that numerous details of the construction shown may be altered or omitted without departing from the spirit of this invention as defined by the following claim.

I claim:

A sound amplifier comprising a conduit having a single passage adjacent its inlet and having an intermediate region Where it is divided into branches which are disposed transversely to said single passage and which are reunited to form another single passage adjacent the outlet of said conduit, said other single passage being located entirely outside the plane of said branches, said conduit being curved between said intermediate region and its outlet to define an enclosed chamber ber, 1926.

' JOHN N. ANDERSON. 

